You may have seen headlines earlier this week about a planet found wandering alone, without a star to orbit. Although that aspect of the new planetary find seems to have grabbed the headlines, it's actually one of the least interesting features of the new find. The body in question awkwardly straddles the border between near-stars called brown dwarfs and giant super-Jupiter class planets, and its features suggest it may have formed through a process identical to one that creates stars. The alternative—that it was ejected from a system of planets that formed orbiting a star—would suggest interstellar space is teeming with rogue planets.

Rogue planets, those that aren't gravitationally bound to a star, have been identified previously through surveys looking for a phenomenon called "microlensing." This occurs when the planet acts as a gravitational lens, briefly brightening a star in the background as the planet passes between the star and Earth. A survey of microlensing objects identified a number of possible planets that mapped to points in space where there were no stars in the neighborhood.

But in this case, the authors managed to directly image one relatively nearby (less than 140 light years away). It happened while they were looking for something else: brown dwarfs. These bodies are large enough to have ignited deuterium fusion (over 13 times the mass of Jupiter), but not large enough to have kicked off sustained fusion of hydrogen. Anything below the brown dwarf cutoff is considered a planet (with the largest of these gas giants typically termed "super Jupiters").

Although that makes for a nice, exact definition of what constitutes a planet, it actually may obscure a more relevant distinction. Normally, we think of stars as forming through the collapse of a gas cloud; planets form through an aggregation of material within the disks that typically surround a star. But as the authors note, that distinction is being challenged by a number of rogue, sub-stellar objects likely to have formed through a process similar to how stars are produced.

When the authors came across CFBDSIRJ214947.2-040308.9 (CFBDSIR2149 to its friends), it first looked like a brown dwarf gradually losing its heat after having ended fusion a while back. But a careful analysis of the light emitted by the object suggested a possible alternative: it was small, too small to have ever undergone fusion. Instead, the heat given off by the object was residual energy from the gravitational collapse of its formation. Further supporting a young age, the researchers found the object appeared to be associated with a small cluster of stars that were all relatively young, between 50 and 120 million years of age.

Based on the composition of the stars and the object's atmospheric properties, the authors conclude it's probably only four to seven times the mass of Jupiter. That's far too small to have ever initiated fusion.

Because it's not associated with any stars, the authors were able to get some detailed information about its atmosphere, spotting indications of methane and potassium in its gaseous envelope. They suggest further observations could use CFBDSIR2149 as an example exoplanet to prepare for the direct imaging of objects orbiting nearby stars. The details we get from those studies could also help us refine the models we have of exoplanet atmospheres.

Given its young age and lack of clear association with any other stars, the authors conclude it probably formed through the collapse of a star-forming gas cloud, rather than within a planetary disk. And if that's the case, they suggest we might want to revisit a lot of the other objects that were initially described as brown dwarfs. It may turn out that some of these actually fall into the planetary mass range. There have been a couple other reports of planet sized objects that formed this way, but we haven't really incorporated this into our models for star formation (the paper suggests that the same sort of fragmentation of gas clouds that leads to binary systems can take place on a smaller scale).

The alternative explanation for this class of object (which the authors call an isolated planetary mass object, or IPMO) is ejection from a system of planets formed from a planetary disk. Models of orbital dynamics suggest this is possible, either due to interactions among planets or the influence of a nearby star. But it should be much harder to eject a super Jupiter-sized planet. So if these large IPMOs are common, smaller ones should be much, much more common (a trend enhanced by the fact smaller planets form in larger numbers). "This would mean," the authors conclude, "free-floating, frozen-down versions of Jupiters, Neptunes, and perhaps Earths are common throughout the Milky Way interstellar ranges."

Promoted Comments

A small side story:I work in the field of infrared optics, and recently while searching for papers I found out that a lot of the cutting edge work was done under the ESA's Darwin project's search for extraterrestrial life. Basically carbon dioxide and water have far IR signatures, so the idea was to look at distant planets with 3-4 infrared telescopes at the second Lagrange point, and using interferometry search for carbon and water signatures. The entire idea was so amazingly cool, and if it had all been done it would have been the next Curiosity. However the sad part is that the project was aborted in 2007 because of lack of funding.We fight wars, kill people, massage our ego, all on this pale blue dot, while the universe awaits us, and we shut it off.When I found out today that the Darwin project was scuttled, a small part of me died today.

If there were enough such planetary bodies running around to be (all the) dark matter there would have to be so many of them that imaging quasars, etc. would be impossible. Furthermore, evidence points to the fact that dark matter does not interact with EM fields at all. Rogue planets certainly do - as they were imaging this one.

Also, thank goodness for Ars for taking their time to cover this a little more completely than popular news outlets. The best anybody else did was to call it a rogue planet and make odd allusions to Melancholia (to those who haven't seen it: just don't).

If there were enough such planetary bodies running around to be (all the) dark matter there would have to be so many of them that imaging quasars, etc. would be impossible. Furthermore, evidence points to the fact that dark matter does not interact with EM fields at all. Rogue planets certainly do - as they were imaging this one.

Well move it outside the galaxy (in the halo) or around the Andromeda galaxy or a distant cluster and see if you can still detect it.

I'm a little troubled by the illustration that goes with the article. It's a rendering, not an image of the body in question and that's not made clear. The link associated with the image points back to Ars.

This is confusing and not good journalism. The actual image is just about a point source.

Good science reporting requires being up front about what's real and what's imagined.

Based on the composition of the stars and the object's atmospheric properties, the authors conclude it's probably only four to seven times the mass of Jupiter.

This part seems a bit 'iffy' to me.

How do they determine the composition? And if this is the first such object found, there can be no established was to correlate composition to mass.

Well.. I'm (definitely) no expert... but I believe they can tell the composition of chemicals/materials by examining the color spectrum? At least, that's what I recall reading in many articles like this -

I'm a little troubled by the illustration that goes with the article. It's a rendering, not an image of the body in question and that's not made clear. The link associated with the image points back to Ars.

This is confusing and not good journalism. The actual image is just about a point source.

Good science reporting requires being up front about what's real and what's imagined.

I'm a little troubled by the illustration that goes with the article. It's a rendering, not an image of the body in question and that's not made clear. The link associated with the image points back to Ars.

This is confusing and not good journalism. The actual image is just about a point source.

Good science reporting requires being up front about what's real and what's imagined.

The URL is in the image caption. Someone just mangled the code. If you copy and paste the URL, you get this:

"Caption: This artist's impression shows the free-floating planet CFBDSIR J214947.2-040308.9. This is the closest such object to the Solar System. It does not orbit a star and hence does not shine by reflected light; the faint glow it emits can only be detected in infrared light. Here we see an artist’s impression of an infrared view of the object with an image of the central parts of the Milky Way from the VISTA infrared survey telescope in the background. The object appears blueish in this near-infrared view because much of the light at longer infrared wavelengths is absorbed by methane and other molecules in the planet's atmosphere. In visible light the object is so cool that it would only shine dimly with a deep red colour when seen close-up.

It is absolutely an artist impression, because as cdcIndc wittily pointed out, the actual photographs of these things are really not viewable by the eye and you can't exactly go CSI Magnify on astronomy images.

I'm a little troubled by the illustration that goes with the article. It's a rendering, not an image of the body in question and that's not made clear. The link associated with the image points back to Ars.

This is confusing and not good journalism. The actual image is just about a point source.

Good science reporting requires being up front about what's real and what's imagined.

image:

Spoiler: show

.

.....leaves a bit to be desired.

Also note the cititation. That image is an artist's conceptual rendering, and has been used by practically every news outlet talking about the story. Keep in mind that the science community is somewhat dependant upon public funding, which is driven by people who are quite certain that shooting a gas cap makes a car explode with enough compressive force to flip the entire car.

Based on the composition of the stars and the object's atmospheric properties, the authors conclude it's probably only four to seven times the mass of Jupiter.

This part seems a bit 'iffy' to me.

How do they determine the composition? And if this is the first such object found, there can be no established was to correlate composition to mass.

Well.. I'm (definitely) no expert... but I believe they can tell the composition of chemicals/materials by examining the color spectrum? At least, that's what I recall reading in many articles like this -

They can tell the temperature of the object and the composition of the radiating surface, but what will this tell them about the size and composition of the core, or the composition of any layers? The internal structure and composition could be inferred, but not measured.

If there were enough such planetary bodies running around to be (all the) dark matter there would have to be so many of them that imaging quasars, etc. would be impossible. Furthermore, evidence points to the fact that dark matter does not interact with EM fields at all. Rogue planets certainly do - as they were imaging this one.

Not really, an object that far away and that small would be invisible from this far away, it would have no impact on our ability to image anything (light would pretty much just diffract around it... think of trying to see a grain of dust a billion miles away, you can't).

However, it still wouldn't explain all of dark matter, at least according to the theory, as the Big Bang didn't produce enough normal matter to explain all of it, only a tiny part (*if* the numbers and theory are correct). It is, however, almost certainly a small portion of the universe's dark matter (the non-EM stuff is non-baryonic dark matter, which is what most people refer to as "dark matter" in the first place).

It's a well established principal, if I understand properly: they measure the properties of the reflected light to infer the composition of the materials through those properties.

I'm familiar with spectrometry, but in this case we have no reflected light. And the emission spectra would have to be in the low infrared, the object is very cold. I suspect that many of the emission lines normally used would not be present. And at best they will tell you the composition of the surface, not the mass.

I'm a little troubled by the illustration that goes with the article. It's a rendering, not an image of the body in question and that's not made clear. The link associated with the image points back to Ars.

This is confusing and not good journalism. The actual image is just about a point source.

Good science reporting requires being up front about what's real and what's imagined.

Not trying to be a dick or anything, but I think anyone reading this story, at least on this site, is under no impression that the image in question could possibly be anything other than a mock up.

It is absolutely an artist impression, because as cdcIndc wittily pointed out, the actual photographs of these things are really not viewable by the eye and you can't exactly go CSI Magnify on astronomy images.

My wife watches CSI (there are several of them), and these guys (and gals) are good. They could not only extract the planetary images but the license numbers of any occupant's cars and their bank balances.

It's a well established principal, if I understand properly: they measure the properties of the reflected light to infer the composition of the materials through those properties.

I'm familiar with spectrometry, but in this case we have no reflected light. And the emission spectra would have to be in the low infrared, the object is very cold. I suspect that many of the emission lines normally used would not be present. And at best they will tell you the composition of the surface, not the mass.

From the article's abstract:

Quote:

The comparison of our near infrared spectrum with atmosphere models for solar metallicity shows that CFBDSIRJ214947.2-040308.9 is probably a 650−750 K, log g = 3.75−4.0 substellar object... An independent Bayesian analysis from proper motion measurements results in a 87% probability that this free-floating planet is a member of the 50−120 Myr-old AB Doradus moving group, which strengthens the spectroscopic diagnosis of youth. By combining our atmospheric characterisation with the age and metallicity constraints arising from the probable membership to the AB Doradus moving group, we find that CFBDSIRJ214947.2-040308.9 is probably a 4−7 Jupiter mass, free-floating planet

It's a combination of spectrometry, knowledge of the composition of the local group, and some modeling.

I'm a little troubled by the illustration that goes with the article. It's a rendering, not an image of the body in question and that's not made clear. The link associated with the image points back to Ars.

This is confusing and not good journalism. The actual image is just about a point source.

Good science reporting requires being up front about what's real and what's imagined.

Really?!

You remind of that guy who didn't like Saving Private Ryan because there was no titles at the beginning of the movie explaining what the boys were fighting for.

Really?

Some things should be self evident.

This is a nerd/science site, not Fox News. It's assumed that everyone reading this would know that the picture above is a rendering. We can't possibly image planets outside our solar system with such precision. We can't at all image most of the 800+ extrasolar planets discovered thus far. We managed to directly observe only a few, and even then it's literally just 4 bright pixels amongst the darkness.

That picture is such an obvious rendering that it needs no explanation.

It's a well established principal, if I understand properly: they measure the properties of the reflected light to infer the composition of the materials through those properties.

I'm familiar with spectrometry, but in this case we have no reflected light. And the emission spectra would have to be in the low infrared, the object is very cold. I suspect that many of the emission lines normally used would not be present. And at best they will tell you the composition of the surface, not the mass.

Give it a rest, kid. You are familiar with spectrometry because you googled it just now after someone told you how they determined the composition of that planet.

I doubt that. Isnt dark matter supposed to be something like 70% of the universe's mass? If it existed as familiar particles (not WIMPS), I rather doubt they would be responsible for the galactic mechanics we observe; they would probably be clumping together.

If that were true, then perhaps stars are born of clumping smaller failed-stars (brown dwarfs) that were, themselves, constructed of clumping super-Jupiters, which were, themselves, constructed of normal Jupiters, et cetera...

It's a well established principal, if I understand properly: they measure the properties of the reflected light to infer the composition of the materials through those properties.

I'm familiar with spectrometry, but in this case we have no reflected light. And the emission spectra would have to be in the low infrared, the object is very cold. I suspect that many of the emission lines normally used would not be present. And at best they will tell you the composition of the surface, not the mass.

From the article's abstract:

Those DOI links almost never work, I've stopped clicking them. And even worse, often when they do work the article is more informative (not always, but often).

Quote:

Quote:

The comparison of our near infrared spectrum with atmosphere models for solar metallicity shows that CFBDSIRJ214947.2-040308.9 is probably a 650−750 K, log g = 3.75−4.0 substellar object... An independent Bayesian analysis from proper motion measurements results in a 87% probability that this free-floating planet is a member of the 50−120 Myr-old AB Doradus moving group, which strengthens the spectroscopic diagnosis of youth. By combining our atmospheric characterisation with the age and metallicity constraints arising from the probable membership to the AB Doradus moving group, we find that CFBDSIRJ214947.2-040308.9 is probably a 4−7 Jupiter mass, free-floating planet

It's a combination of spectrometry, knowledge of the composition of the local group, and some modeling.

1. If it was just discovered they can't have a very good measure of it's "proper motion". But I would think it close enough for this method.2. So basically it would seem that the question is, given the current temperature, at what mass would the heat of formation cool to the current temperature given an age of 50-120 million years. I guess there are some more assumptions about it's size (but this is well understood I would think).

I doubt that. Isnt dark matter supposed to be something like 70% of the universe's mass?

They got that covered, they say that there are tons of these littering the galaxy.

-- But it should be much harder to eject a super Jupiter-sized planet. So if these large IPMOs-- are common, smaller ones should be much, much more common (a trend enhanced by the-- fact smaller planets form in larger numbers). "This would mean," the authors conclude, -- "free-floating, frozen-down versions of Jupiters, Neptunes, and perhaps Earths are common-- throughout the Milky Way interstellar ranges."

I've demangled the code, and appreciate the fact that at least some people don't think we're destroying journalism every time we reverse the fields where different text belongs in our content management system.

So, should one of these pass close enough to a star it might be captured and settle into an orbit around it, yes?

It would be interesting to see what effect it would have on any existing planets in that system. Given the distances and forces involved in, for example, our own solar system, would there be much, if any?

I'm a little troubled by the illustration that goes with the article. It's a rendering, not an image of the body in question and that's not made clear. The link associated with the image points back to Ars.

This is confusing and not good journalism. The actual image is just about a point source.

Good science reporting requires being up front about what's real and what's imagined.

Perhaps I should ask the reverse of the original...Why was it assumed that every gas cloud was automatically big enough to collapse into a full star?

It wasn't. Indeed, this sort of thing isn't a new idea at all (despite being presented as "news"); we've been expecting that something like this would be found for ages.

There is actually a minimum mass for such objects (I don't recall what it is; maybe around 1 Jupiter mass? Don't quote me on that) but yeah, its expected that such things could have formed. Indeed, some "planets" around other stars have been speculated to have been failed binaries, more or less.

I'm a little troubled by the illustration that goes with the article. It's a rendering, not an image of the body in question and that's not made clear. The link associated with the image points back to Ars.

This is confusing and not good journalism. The actual image is just about a point source.

Good science reporting requires being up front about what's real and what's imagined.

image:

Spoiler: show

.

.....leaves a bit to be desired.

Also note the cititation. That image is an artist's conceptual rendering, and has been used by practically every news outlet talking about the story. Keep in mind that the science community is somewhat dependant upon public funding, which is driven by people who are quite certain that shooting a gas cap makes a car explode with enough compressive force to flip the entire car.

A much larger percentage of the audience is aware that Hollywood explosions are not realistic and suspension of disbelieve is for enjoyment of the film than you imply.

Also note the cititation. That image is an artist's conceptual rendering, and has been used by practically every news outlet talking about the story. Keep in mind that the science community is somewhat dependant upon public funding, which is driven by people who are quite certain that shooting a gas cap makes a car explode with enough compressive force to flip the entire car.

A much larger percentage of the audience is aware that Hollywood explosions are not realistic and suspension of disbelieve is for enjoyment of the film than you imply.

Then I envy you for being surrounded by a much more well-informed public than I